1. Technical Field
The present invention relates to an adaptive cruise control system according to the preamble of claim 1 and a method for controlling the velocity of a motor vehicle. The invention also relates to a computer program comprising computer program code for implementing the method, a computer program product comprising a data storage medium readable by an electronic control unit and having said computer program stored thereon, and an electronic control unit.
2. Background Art
An adaptive cruise control system for use in motor vehicles is previously known, e.g. from US 2003/0204298 A1. The motor vehicle provided with the adaptive cruise control system is in the following referred to as the “host vehicle”. Under driving conditions with no other vehicle within a certain range in front of the host vehicle in the predicted travelling path thereof, the adaptive cruise control system, when activated by the vehicle driver, influences the operation of the host vehicle so as to keep the velocity of the host vehicle essentially equal to a desired vehicle velocity set by the driver, in the following referred to as the “set vehicle velocity”. Under said driving conditions, the adaptive cruise control system operates in a conventional cruise control mode. When an obstructing object, such as another motor vehicle, travelling in the predicted path of the host vehicle at a velocity lower than the set vehicle velocity of the host vehicle is detected within the above-indicated range, the adaptive cruise control system reduces the velocity of the host vehicle and makes the host vehicle follow the detected object at a desired distance from it, i.e. the adaptive cruise control system will in this case influence the operation of the host vehicle so as to keep the host vehicle at a desired distance from the detected object. A detected object travelling in the predicted path of the host vehicle is in the following referred to as “target object” and said desired distance is in the following referred to as the “set distance”. When the obstructing target object is accelerated to a velocity above the set vehicle velocity of the host vehicle or when it for any reason no longer is detectable in the predicted travelling path of the host vehicle and no other obstructing target object is detected, the adaptive cruise control system resumes the cruise control mode and accelerates the host vehicle back to the set vehicle velocity.
When a host vehicle under the control of an adaptive cruise control system is following a first vehicle at the set distance from it and is overtaken by a second vehicle that turns in between the host vehicle and the first vehicle and keeps a velocity higher than the set vehicle velocity of the host vehicle, the adaptive cruise control system will initiate an acceleration of the host vehicle so as to accelerate it back to the set vehicle velocity. In this situation the driver of the second vehicle has two main options: either overtake also the first vehicle, or stay behind the first vehicle and thus reduce the velocity of the second vehicle to the velocity of the first vehicle. If the first option is chosen, the accelerated or accelerating host vehicle might get undesirably close to the first vehicle when the first vehicle is overtaken by the second vehicle and it might be necessary for the driver of the host vehicle to manually activate the brakes of the host vehicle, which will deactivate the adaptive cruise control system. If the second option is chosen, the accelerated or accelerating host vehicle might get undesirably close to the retarding second vehicle and it might also in this case be necessary for the driver of the host vehicle to manually activate the brakes of the host vehicle, which will deactivate the adaptive cruise control system. There is also a risk of a dangerous accident in a situation of this type due to the undesired acceleration of the host vehicle.